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Let's talk about modules.

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So in Python, there's these two similar but kind of different

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concepts. There's this one called a module, and there's one called a package.

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In the last few lessons, we were talking about packages.

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So now let's talk about modules.

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So a module is really just a different '.py' file.

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So if you've got another '.py' file, and you're importing anything

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from it, that's called a module.

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And a package is usually a whole system of files.

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It's a whole bunch of modules, or a whole bunch of Python

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files put together,

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and you can usually install a package with 'pip install', and

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then the package name, 'packagename'.

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But a module can simply be one file or a few files.

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And the idea behind a module is really just to separate your

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code into smaller files instead of having one massive Python

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file. So we've seen some code in our Jupyter Notebook, and

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that code really didn't get too long.

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But in real life, you might end up having a file that has

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a 1000, 2000, 14000 lines of code in it.

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And if you ever see something like that, that is a really

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good candidate for pulling out some of that code and putting it

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into another file.

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So let's go ahead and make a little example here.

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I'm going to create a new file, and I'm going to save this

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as 'custom_module.py',

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and I'm going to put that up just on my Desktop here,

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'custom_module.py'.

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And I'm going to create a new function.

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So 'def my_greeting():', I guess.

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And it's just going to say, 'print("Hello from custom_module.

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[no audio]

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Now I'm going to create another file, but this one is

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going to be called 'my_program.py'. 'my_program.py'.

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And let's go ahead and oops, there is no folder in there.

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So let's hide that.

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And let's go ahead and reopen that other file.

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So we have 'custom_module' and 'my_program.py' in here.

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And let's label these as well, '#custom module',

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and this one is, I'll delete that, '#my program'.

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So because these live side by side, what I can do is import

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one from the other.

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So in my program, I can say 'from custom_module import',

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and then I can import this particular function, and then I can

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run it in here.

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'my_greeting()', run.

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Now let's go into our terminal here, and I'm going to 'cd'

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into my Desktop, because that's where my files are.

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And if I do 'ls -la', we'll see we've got 'my_program' from a previous

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video, we also have 'custom_module', and 'my_program'.

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So let's go ahead and run 'my_program'. 'python

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my_program.py', and it says, "Hello from custom_module.py".

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So 'my_program' actually doesn't have a 'print' statement in here at all.

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What it's saying is from the 'custom_module' import this particular

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function. Look at that, 'custom_module.py'

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actually has this function, and it ran the 'print' statement.

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And that's all there is to making a module. It's really, you're just

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moving one bit of Python to another file.

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Now, I would like you to give this a shot. Create two Python

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files, and import a function from one of those, and run it

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in a different file. So you can even copy what I have, 'my_program.py',

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and 'custom_module.py',

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and you can just have 'my_greeting' in there.

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Go ahead and 'import my_greeting', and then execute it.

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And again, there's no 'print' statement in here.

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It is running the code from this file.

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It's just moving it into here, and executing it.

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Go ahead and give that a shot.

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And once you are done with that, let's head on over to the

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next lesson where we are going to create a package.